10 DIMORPHIC BRANCHES IN TROPICAL CROP PLANTS. 



in the individual plant with the successive links of the chain of organic 

 development led Goethe to the view that each plant is an evidence of a 

 general law of evolution. 



Every plant will declare it, the law of the endless creation, 

 Every flower will repeat it, louder and louder the voice. 



SIMILARITY OF DIMORPHIC BRANCHES TO ALTERNATING 



GENERATIONS. 



Darwin also recognized the individuality of the internodes of plants, 

 though apparently without attaching an evolutionary significance to 

 the fact, no reference being made to it in " The Origin of Species." 

 Attention has been called by Mr. Argyle McLachlan to an interesting 

 paragraph in another work, in which Darwin draws a comparison 

 Ijetween the leaf buds of plants and the individual animals that build 

 up the branching colonies of zoophytes: 



The examination of these compound animals was always very interesting to 

 me. What can be more remarkable than to see a plant-like body producing an 

 egg, capable of swimming about and of choosing a proper place to adhere to, 

 which then sprouts into branches, each crowded with innumerable distinct 

 animals, often of complicated organizations. The branches, moreover, as we 

 have just seen, sometimes possess organs capable of movement and independent 

 of the polypi. Surprising as this union of separate individuals in a common 

 stock must always appear, every tree displays the same fact, for buds must be 

 considered as individual plants. It is. however, natural to consider a polypus, 

 furnished with a mouth, intestines, and other organs, as a distinct individual, 

 whereas the individuality of a leaf bud is not easily realized; so that the union 

 of separate individuals in a common body is more striking in a coralline than 

 in a tree. Our conception of a compound animal, where in some respects the 

 individuality of each is not completed, may be aided by reflecting on the produc- 

 tion of two distinct creatures, by bisecting a single one with a knife, or where 

 nature herself performs the task of bisection. We may consider the polypi in 

 a zoophyte, or the buds in a tree, as cases where the division of the individual 

 has not been completely effected. Certainly in the case of trees, and judging 

 from .-iiialogy in that of corallines, the individuals iiropagated by buds seem more 

 intimately related to each other than eggs or seeds are to their parents. It 

 seems now pretty well established that plants propagated by buds all partake of 

 a common duration of life, and it is familiar to every one what singular and 

 numerous peculiarities are transmitted with certainty by buds, layers, and 

 grafts, which by seminal propagation never or only casually reappear.'' 



It is plain from this passage that Darwin considered the internodal 

 structure of plants as a method of vegetative propagation of new 

 individuals rather than as an example of successive stages of evolu- 

 tionary progress. This becomes the more evident from his compari- 

 son of the results of vegetative propagation with those obtained by 

 sexual reproduction. The general tendency to uniformity among 

 vegetative individuals lends greater significance to differences that 



" Darwin, Charles. Journal of Researches, end of chapter 9. 

 198 



